This invention relates to an apparatus for detecting the passage of multiple superposed documents along a feed path, such an apparatus being often referred to as a double detect device.
As the automatic transporting and processing of documents such as currency notes or checks has grown in recent years, the need has increased for a simple and reliable means requiring minimal adjustment for detecting when a document, such as a currency note in an automatic cash dispensing machine or a check in a check sorting machine, has become superposed on another, since such superpositioning may produce undesirable results such as the dispensing of an excessive amount of money from an automatic cash dispensing machine.
Various double detect devices have been proposed. For example, in operation of one known double detect device currency notes are fed between a pair of gauging rollers. In the event of multiple notes (or an excess thickness note) passing between the rollers, the axis of one of the rollers is displaced by an amount such that a note rejecting means is actuated, actuation of the rejecting means causing the notes or note to be diverted into a reject hopper. This known device has the disadvantage that it does not distinguish between superposed notes and a single note having a localized increase in thicknes, brought about for example by a crease or fold in the note or by the attachment thereto of extraneous matter such as adhesive tape. As a result, there is a tendency for such known device to reject an excessive number of notes, and the use of such device in an automatic cash dispensing machine would tend to increase maintenance costs, since the rejection of an excessive number of notes would decrease the period of time between successive replenishments of the machine with currency notes.